Benchmark Description

This benchmark measures the scp performance
between two systems
with variable router delays in the network between the two
systems.
A file size of 48 MB was used while measuring the affects of
varying the latency (network delays) and varying the
TCP receive window size.

Key Points and Best Practices

The WAN emulator (aka. hxbt) is used in the router to achieve
delays. Verification of network function and characteristics confirmed
after setting the simulator using Netperf latency and bandwidth tests
between driver and test system.

Transfers performed over 1 GbE private, dedicated network.

Files were transferred to and from /tmp (i.e. in memory) on the
test systems to minimize effect of filesystem performance and variability on
the measurements.

Larger TCP receive windows than default can be enabled using the system-wide
parameter tcp_recv_hiwat (e.g. to enable 1024 KB windows using
this method, use the command:
ndd -set /dev/tcp tcp_recv_hiwat 1048576). To make this change
persistent the command will have to be added to system startup scripts.

sshd on target system must be restarted before any benefit can be
observed after increasing the enabled tcp receive buffer size.
(e.g: can restart with the command
/usr/sbin/svcadm restart svc:/network/ssh:default)

Note that tcp_recv_hiwat is a system-wide variable that adjusts
the entire TCP stack. Care, therefore, must be taken to make sure that changes
do not adversely affect your environment.

Geographically distant servers can be affected by connection latencies of the kind presented here.

See Also

Disclosure Statement

Copyright 2013, Oracle and/or its affiliates. All rights reserved.
Oracle and Java are registered trademarks of Oracle and/or its
affiliates. Other names may be trademarks of their respective owners.
Results as of 2/08/2013.

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BestPerf is the source of Oracle performance expertise. In this blog, Oracle's Strategic Applications Engineering group explores Oracle's performance results and shares best practices learned from working on Enterprise-wide Applications.